(1) Field of the Invention
The present invention relates to a method of determining the type and root of a chord, comprising at least two and at most four notes, which is played on a musical instrument, particularly an electronic keyboard type instrument. More specifically, this invention is directed to logic circuitry for analyizing chords played on a keyboard instrument and producing a digitally coded output signal from which the appropriate sound may be synthesized. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
The determination of the type and root of a chord comprising two to four notes, played on a chromatically tuned electronic keyboard instrument, is required in order to, by way of example only, produce an automatic accompaniment to a melody "voice" simultaneously played on the instrument. It has been prior art practice to convert all chords which were played into digital data and to employ the thus produced data to address a read-only memory in which all possible chord types and roots were stored. Thus, in a typical prior art electronic organ, if the chord C-E flat was played, the memory would be addressed with the coded information "minor chord with root C." While this is an operable approach to the synthesis of sound corresponding to keyboard manipulation, it is also an unwieldy approach since the identification method necessitates a very substantial memory capacity. The requirement of a large memory for chord identification is an obvious disadvantage from the standpoint of equipment complexity and cost.